Back in the '70s, the world was content to
store its computer information on floppy disks. They were cheap,
marginally reliable and easily transported from machine to machine.

With the '80s came a new technology, the Winchester drive.
Portability was sacrificed, but in most minds it was for a worthy cause:
spectacular gains in storage capacity and access speed.

But the NeXT Computer is focused on the 90's, and demands a new level
of performance. It offers a method of storage that is simultaneously
vast, reliable, transportable and cost-effective - a combination unmatched
by computers of any size.

It's a storage technology that is bound to become the standard
technology of the '90s: the read/write/erasable optical disk.

In an optical drive, there is no danger of head crashing; data is both
written and read via laser. The optical disk itself can be erased
and rewritten over and over, with no degradation over time.

Like a floppy, the optical disk is removable. Not only does it
provide simple portability from one machine to the next, it provides a
high degree of security, in that a user can maintain personal possession
of important work.

A single NeXT optical disk offers 256
megabytes of storage. By providing such a huge capacity to every computer
user, NeXT is removing a major obstacle to the everyday use of files
containing high-resolution graphics and digital sounds- either of which
can display quite an appetite for valuable disk space.

Further, a single optical disk can
store a user's entire world. That includes the operating system,
applications, fonts, data files, manuals, even a library of reference
books. With such a disk a user can sit down at any NeXT computer and
instantly be working in a personalized computing environment. One disk can
literally contain the totality of a student's college work, as well as a
complete dictionary, thesaurus and other resources vital to a particular
field of study. Or, in a business setting, a single disk can store
hundreds of thousands of customer records, along with often-used corporate
reference materials.

To say that the optical drive provides
infinite storage is not an exaggeration. If one disk eventually
becomes full, another can easily be inserted in its place. In this
way, optical disks offer an extremely low-cost method of storing massive
amounts of data.

The NeXT Computer offers Winchester
storage as a supplement to its optical technology. High-capacity
hard disks are currently available, so its possible configure your NeXT
system to allow access to truly enormous amounts of storage - approaching
one gigabyte and more - without adding a single external device.

As the first computer to come standard
with an optical drive, the NeXT System becomes the first to offer a viable
means of getting mass storage in and out, quickly and reliably. With
this technology in place, NeXT now brings a new order of magnitude to the
things a computer can do.

The Optical Drive: A Guided Tour.

The optical disk rotates at a brisk 3000 revolutions per minute.
Like a compact disc, it has a layer of reflective aluminum backing, on top
of which is a magneto-optical substrate. This substance is comprised
of crystals that actually hold the information. True to digital
tradition, information on an optical disk exists as either of two values,
"0" or "1". The value is determined by the
magnetic orientation of the crystals. Unlike a floppy or Winchester
disk, an optical disk cannot be altered by a magnetic field alone.
At normal temperatures, the orientation of its crystals remains locked.

Read and write operations are performed by a single laser. Before
new data is written, an "erase" process takes place. An
electromagnetic device activates, preparing to orient susceptible crystals
to the "0" position. The laser then focuses on the
substrate, heating it to its Curie point" (If your physics is
rusty, that's the temperature at which the crystals in the substrate
"unlock," and allow themselves to be reoriented in the presence
of the magnetic field.) In this manner, all portions of the disk to
be written are erased.

Next comes the writing procedure. The magnetic field is reversed
so that it will reorient those sections of the substrate that reach the
Curie point to the "1" position. Every spot to be set to
the "1" value is then heated by the focused laser. Upon
completion of the writing procedure, a second pass is made to verify
accuracy.

In reading data, the magnetic field is turned off. A low-level
laser is aimed at the disk, traveling through the substrate and reflecting
off the aluminum backing. Enter the Kerr effect - in which the
alignment of the crystals in the substrate alters the polarization of the
reflected beam. The beam travels through a polarizing filter to a
photodetector, and the intensity of the beams determines whether
"0" or "1" was read at that particular spot on the
optical disk. Simple.

The NeXT optical disk provides mass storage that is portable, reliable
and cost-effective. It is shown here in its actual size.